Does IERS belong in astropy.utils

Sorry if I'm late to comment on this.

It seems to me that `astropy.utils.iers` doesn't belong under `astropy.utils`, which is defined as:

```
This functionality is not astronomy-specific, but is intended primarily for use by Astropy 
developers. It is all safe for users to use, but the functions and classes are typically 
more complicated or specific to a particular need of Astropy.
```

I think it should probably either be a subpackage of time (which is where it is primarily used), or its own top-level package, but I see `utils` as primarily software engineering bits of stuff.